1. Field of the Invention
The present invention relates to a chest brace and method of using a chest brace to prevent collapse of a chest wall of a patient, such as a neonate, to keep the lungs inflated. More particularly, the present invention pertains to an inexpensive chest brace that interacts with the skin covering the chest, rather than through applied negative air pressure, to provide a distending force on the chest wall to prevent its collapse, especially during respiration.
2. Description of the Related Art
Pulmonary insufficiency associated with immaturity is one of the most common life-threatening hurdles that confronts the premature newborn baby. The newborn""s rib cage is soft and buckles easily during spontaneous respiration, particularly during inspiration. Underdevelopment of the intercostal muscles, lungs, or both contributes to the chest""s deformability. In premature infants below 30 weeks gestation, thoracic wall elastic recoil is almost non-existent, so that the resting volume of the lungs is very close to or below their collapsed volume. Also, the relatively compliant chest wall tends to collapse as the diaphragm descends, resulting in a diminished tidal volume. As a result, most premature infants require assisted ventilation or a continuous distending pressure (CDP).
Continuous positive airway pressure (CPAP) is widely established as an effective method for preventing lung wall collapse, chest wall distortion, and for increasing oxygenation. Currently, CPAP is used almost exclusively in preference to continuous negative distending pressure. CPAP, however, is potentially hazardous to newborn infants with weakened respiratory systems. It is usually administered by nasal prongs, but has major limitations and serious side effects. These include: nasal trauma, difficulty in obtaining a good fit in very small infants, and high gas flows that cause airway cooling, drying, and obstruction of the nasal passages. During periods of crying and mouth opening, especially with high CPAP flows, there is a loss of pressure and the infant inhales room air. Frequent dislodgement of the nasal prongs makes nursing difficult, especially when associated with repeated bouts of desaturation. High or fluctuating saturation may increase the risk of retinopathy. Perhaps more serious are the circulatory disturbances, decreased venous return to the heart, diminished cardiac output, and increased intra-cranial hemorrhage.
Negative pressure applied intermittently around the chest has been used for more than a 100 years as a way of assisting ventilation in patients with respiratory failure. The iron lung is perhaps one of the best recognized negative pressure ventilators. Continuous negative distending pressure (CNP) is used to manage a number of specific conditions that produce respiratory failure in neonates and older infants. Negative distending pressure is highly effective and does not have many of the side effects of CPAP. Among its benefits with patients with respiratory disease syndrome are an increase in resting volume of the lung and arterial oxygen tension. There is also no need for an airway or nasal prongs. As opposed to positive distending pressure, CNP produces a decrease in intrathoracic and right arterial pressures, favoring venous return to the heart from parts of the body that are not exposed to the negative pressure. CNP further increases lung lymph flow and lung albumen transport. CNP also avoids the increases in pulmonary vascular resistance and pulmonary artery pressure that are observed with positive airway pressure. Recently, CNP has been re-introduced to treat infants with various pathological conditions.
While improvements have been made in the design of devices for generating extra-thoracic negative pressure, the devices are still difficult to attach to small newborns. Current designs consist of a cuirass or chamber and use vacuum around the chest or lower body to generate negative pressure. These devices require some form of electrical power supply, are relatively expensive, and are cumbersome. Technical difficulties are associated with temperature control, neck seals obstructing venous return, leaks around the seals and limited patient access. These devices also require considerable training and experience to operate and the technical problems make nursing difficult and frustrating. This limits the use of a potentially life saving treatment modality.
There are also situations where the thoracic shape of the newborn is not within normal thresholds, regardless of whether or not the chest is collapsing during respiration. A normal, healthy infant has a thoracic index between approximately 85%-95%. Thoracic index is defined as the ratio of the height of the chest, i.e., in an anterior-to-posterior direction or vice versa, over the width of the chest, i.e., in a lateral or side-to-side direction, when measured in the prone or supine position. Newborns with a thoracic index of less than 65%, for example, are generally not considered healthy. This decrease may or may not be related to collapsing of the chest during respiration. For example, a decreased thoracic index can be due to a malformation, or it may be present simply because the infant""s chest has collapsed to a point at beyond which it can collapse no further. In such infants, there is a need to restore the thoracic index to its normal range. However, conventional assisted ventilation and CNP devices, which used primarily to prevent lung collapse, does little or nothing to improve the infant""s thoracic index.
Accordingly, it is an object of this invention to provide a chest brace that overcomes the shortcomings of conventional techniques for preventing collapse of a patient""s chest during spontaneous inspiration.
It is another object of this invention to provide a chest brace that provides a continuous distending pressure on the patient""s chest so as to correct any collapse that is evident between breaths, i.e., at the end of expiration.
It is still another object of this invention, to provide a chest brace that provides continuous distending pressure on the patient""s chest cavity without requiring vacuum seals.
It is yet another object of this invention to provide a chest brace that is particularly adapted for use with premature newborn babies.
It is still another object of this invention to provide a chest brace that is simple to attach, inexpensive, and does not require electrical power to operate.
It is a further object of the present invention to provide a chest brace and method of using such a brace to improve a patient""s thoracic index even in the absence of chest collapse associated with respiration.
It is still a further object of this invention to provide a chest brace that is adapted to provide intermittent negative pressure ventilation for a patient without a need for endotracheal intubation.
These objects, among others, are achieved, according to one embodiment of the present invention, by providing a chest brace that includes an anterior member adapted to overly a patient""s chest. An adhesive mechanism secures the anterior member to the surface of the patient. A support structure is coupled to the anterior member such that, in use, the support structure imparts a force on the anterior member in a manner so as to distend a thorax of the patient. In one embodiment of the present invention, the support structure includes a posterior member that is coupled to the anterior member using a mechanical linkage, so that the anterior member can be moved relative to the posterior member in a ratchet-like fashion, thereby imparting the distending pressure. This allows the patient to receive the distending force regardless of whether they are in the supine or prone position. In another embodiment of the present invention, the support structure includes a support structure, such as a shield, having a portion that is placed over the patient. The anterior member is suspended from the shield in a manner so as to impart the distending force on the patient""s chest. The present invention also contemplates adhering a chest plate to the patient so that the anterior member can be selectively attached to the patient merely by securing it to the chest plate, thereby avoiding the need to remove the adhesive from the patient each time the patient is removed from the chest plate.
It is a further object of the present invention to provide a method of imparting a distending force on a thorax of a patient that that overcomes the shortcomings of conventional methods for preventing collapse of a patient""s chest, improving the patient""s thoracic index, or both. This object is achieved by providing a method that includes adhesively securing an anterior member of a chest brace structure to a patient""s chest and imparting a force on the anterior member so as to distend a thorax of such a patient. Numerous techniques for imparting a force on the anterior member are discussed in detail below.
These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.